[mike turner]

how can i check this box to see if it is bad ? its a 1983 merc. 70hp. the boat was running fine , then i shut it off and it wouldnt start again. i have no fire from any of the 3 coils. thanx mike

[Bob37814]

Do you have any corroded or broken wires going from the pack itsself or the coils? Check to make sure all wires, including grounds are tight.....Bare wires with insulation falling off or melting can kill a pack quicker than anything

[mike turner]

all wires are in great condition and we checked all grounds. we are a little concerned about the kill switch.

[mark_gober]

Mike,

I don't have that particular motor, but if all three coils aren't firing, I might start looking at the rotor and not the power pack. The power pack does provide fire to all the coils, but they are largely three separate circuits. Your rotor going bad would stop sending signals to the coil and it wouldn't fire any of them.

You might check out this post, although it is for a different HP motor, the concept will still apply.

http://forums.iboats.com/showthread....uble shooting

Mark

[mark_gober]

Mike,

you can test the kill switch. Stick a meter across the wires. If it's bad, (meaning constantly pressed) you should read zero ohms. If it's good, you should read an open. Worst case scenario, you could clip one of the wires and test it. Then just resolder.

Mark

[Bob37814]

Being a 3 cly 83 model, Im thinking this motor would have the alternater driven ignition.....I may be wrong, but just a thought....

[mike turner]

what should i look for at the rotor and what test can i run ?

[mark_gober]

The ideal setup would be to have a o'scope. Now I realize that not everyone has access to this particular piece of troubleshooting equipment. Barring having that, if you place a meter on the leads and look at AC, you should see a change when you crank the engine as the rotor passes the stator. It won't be definitive, but it will tell you whether or not you are getting a pickup.

[mike turner]

ok , i can do that. i should set the multimeter to read 12 volts dc, correct? what range of numbers should i see? question for you ! doesnt a wire from the stater go directly to the switch box? i believe either blue or red . i should be able to check it at the switch box ??? thanx, mike

[CharlieB]

Download the FREE Ignition Troubleshooting Guide by following the link at

www.rapair.com

It contains step-by-step instruction to test and diagnose your complete system.

It is complete down to what color wire to test.

There is no bench test for the box, it is a process of elimination of the rest of the components of the system.

[mike turner]

i am getting voltage into the box but nothing from the three outgoing posts. what is the best way to test those posts? thanx, mike

[Laddies]

Your original question was how to test the box, start with buying a DVA then disconnect the black/yellow lead from the box next test the inputs from the stator inputs red =25v + v./ blue= 180 + v. / each trigger wire +4+ v. and each output should be 150 volt. Not so hard after all.

[mike turner]

thank you, i got 24.5 v from the red , but only 24.7v from the blue, only got 1.2 from each trigger wire, nothing coming out

[Laddies]

Are you using a DVA as the stator voltage sounds low which is not a suprise but the trigger voltage being low I think might be a faults reading as they never have problems in all 3 seperate windings at the same time.

[mike turner]

i appologize, i'm not using a dva, i'm using a fluke multimeter, and i dont have an adapter. i guess the multimeter wont do the job by itself ?

[Laddies]

Mike, you need the DVA to read the peak voltage in the system or it can show a low reading.

[mark_gober]

Laddies,

I've got a DVA question for you? What is in the DVA that allows it to see peak voltage? If you have a true RMS voltmeter (newer one) couldn't you just multiply it by the inverse of .707 and get peak? I've never used a DVA, so I'm unsure as to why you must have one.

Mark

[mike turner]

The one item it didn't test until today is the rectifier. Turns out I do get a bad reading on one of the posts. Could a faulty rectifier prevent the engine from firing?

[Laddies]

Mike, A shorted rectifier can keep a engine from firing but if you disconnect the yellow wires then the spark should return, if the short has not damaged the stator.
Mark, I don't know about the factor for sure but some of todays newest meters are equipt to read peak voltage and can read the system without a DVA.

[three under]

Good stuff! I'm heading home in a couple hours to trouble shoot my 50hp merc that has no spark and I'm gonna add this to my arsonal that I have established by using the search engine on this site the last couple day's. Laddies, your willingness to share your knowledge and help others is much appreciated.

[mike turner]

three under, please share what you may find out. i'm just about at the end of my rope. i cant get my hands on a dva, and its not in the budget to buy one. thanx, mike

[three under]

I will definatly share with you what I find tonight. From what I have read here I strongly suspect it to be the switch box. I have an old style ohms meter with a needle and scale which I am hoping will work better than my digital for this application because I do not have a dva either and my budget for getting this thing running is getting low.

[mike turner]

great thanx, laddies said that a multimeter wont work, and you need a dva. do you think an analog meter will work ?

[three under]

If the purpose of the DVA is to see peak voltage,I'm thinking you can just take the high reading from your analog? Someone please correct me if I'm wrong. That's what I plan on trying tonight.

[mike turner]

my multimeter has a button that you can push and it will hold the highest voltage spike on the screen. sound like that should work, right? i'm sure laddies will have the correst answer for you .